A recent development in the field of electro-mechanics has been the miniaturization of various mechanical devices. Typical of such devices are tiny gears, levers, and valves. These "micro-mechanical" devices are manufactured using integrated circuit techniques, often together with electrical control circuitry. Common applications include accelerometers, pressure sensors, and actuators. As another example, spatial light modulators can be configured from micro-mechanical reflective pixels.
One type of micro-mechanical spatial light modulator is a digital micro-mirror device (DMD), sometimes referred to as a deformable mirror device. The DMD has an array of hundreds or thousands of tiny tilting mirrors. Light incident on the DMD is selectively reflected or not reflected from each mirror to an image plane, to form images. To permit the mirrors to tilt, each is placed on one or more support posts and spaced by means of an air gap, over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. In many DMDs, an edge of the mirror contacts a landing electrode, which serves as a stop.
Reliability has been difficult to achieve with micro-mechanical devices. A common reliability problem is the sticking that may occur when moveable elements contact each other. If such elements stick together, the device ceases to operate properly.
Previous approaches to preventing sticking of contacting elements of micro-mechanical devices have been directed to coating the surfaces of the landing electrode and the mirror. The application of a layer of polymeric material is described in U.S. patent application Ser. No. 08/216,194, now U.S. Pat. No. 5,447,600, entitled "Polymeric Coatings for Micromechanical Devices". The application of a layer of perfluoropolyether material is described in U.S. patent application Ser. No. 08/239,497, entitled "PFPE Coatings for Micro-Mechanical Devices" (Atty Dkt No. TI-18478). It has also been discovered that a monomolecular layer (monolayer) may result in a reduction of friction between the contacting elements, thereby reducing the possibility of sticking. U.S. patent application Ser. No. 07/823,580, now U.S. Pat. No. 5,331,454, entitled "Low Reset Voltage Process for DMD", describes a method of providing a monolayer by means of vapor deposition. Each of these patent applications is assigned to Texas Instruments Incorporated.